Biology Chapter 11 Notes: Communication between yeast cells. Two types of yeast cells a and alpha cells. 1.) Exchange of mating factors Each cell type secretes a mating factor that binds to the receptors on the other cell type. Yeast cell a will release a signalling factor called a factor which will bind to the specific receptor on the alpha cell, same thing with alpha cell. 2.) Mating Binding of the factors to receptors induces a change in the cells that leads to their fusion 3.) New alphaa cell is formed with the fusion of the two nuclei from the previous cells which now include all DNA of both cells. Local and Long Distance Signaling: Local signaling involves sending messenger molecules, signalling molecules, to nearby places which influence other cells. Some of these travel only short distances such as local regulators which influence cells in the nearby vicinity. One class of local regulators in humans are called growth factors which stimulate nearby target cells to grow and divide. Synaptic signalling occurs in the animal nervous system. An electrical signal along a nerve cell triggers the secretion of neurotransmitter molecules carrying a chemical signal. These molecules diffuse across the synapse, triggering a response in the target cell. Long distance signaling involves sending hormones which travel via the circulatory system to other parts of the body where they reach target cells that can recognize and respond to the hormones. This is called endocrine signalling. 3 Stages of Cell Signaling: 1.) Reception It is the target cells detection of a signalling molecule coming from outside the cell. A chemical signal is detected when the signalling molecule binds to a receptor protein located at the cells surface or in the cell. 2.) Transduction The binding of a signalling molecule to a target molecule initiates a change in the target molecule which converts the signal to a form that can bring about a specific cellular response. Transduction can be in one step or can occur in multiple steps through a signal transduction pathway. 3.) Response The signal is converted into a cellular response. Response can be any activity ranging from phosphorylation to enzyme catalysis.